An extended DNA undergoes linking number accumulation when one end of the DNA is rotated while the other end is kept fixed, as shown in Fig.REF . The stretching force \(f=0.5 pN\) , the rotation angle \(\Omega =\omega t\)  and the angular velocity \(\omega =20\pi /s\) , equivalent to \(\Delta Lk=10\)  per second (i.e., comparable to polymerase enzyme unwinding and synthesizing at  100 nucleotide or nt per second)[1]}, [2]}. At first, the extended DNA is twisted, and then it undergoes a buckling transition (discontinuities on torque and extension curves) followed by plectoneme formation[3]}.
